Market-order costs: trading fees, spread and average fill price
A fee schedule covers only part of an execution comparison. Price deviation depends on direction, size and available depth. Keep that estimate separate from your account’s trading fee and use the same benchmark across venues.
At an assumed trading fee of 0.05%, the fee is 1,002.80 × 0.05% = 0.5014 USDT.
Walk through a three-level order book
Assume a mid-price of 100.00 USDT and a purchase of 10 units. Available asks are 2 units at 100.10, 3 at 100.20 and 5 at 100.40. The simulated purchase spends 200.20 + 300.60 + 502.00 = 1,002.80 USDT. Its average price is 100.28, or 28 basis points above the mid. All prices and quantities in this example are hypothetical.
Worked example · not a live quote
Buying 10 units through three levels
| Ask (USDT) | Quantity | Fill value (USDT) |
|---|---|---|
| 100.10 | 2 | 200.20 |
| 100.20 | 3 | 300.60 |
| 100.40 | 5 | 502.00 |
Add the fee without counting spread twice
At an assumed trading fee of 0.05%, the fee is 1,002.80 × 0.05% = 0.5014 USDT. Against a 1,000 USDT mid-price benchmark, price deviation plus fees totals about 3.3014 USDT. The deviation from mid already includes crossing the spread; adding the full spread again would double-count it. A benchmark based on best ask or decision-time price produces a different slippage measure.
An incomplete fill is not a complete quote
If the order were for 12 units but only 10 were visible, the last two units have no known execution price. The average for the first ten cannot represent the whole order. Venue protections may constrain market orders. Even sufficient displayed depth can be canceled or consumed before an actual order arrives, so this site’s book simulation is not an execution guarantee.
Compare like with like
A sell consumes bids, not asks. A small order is not a proxy for a large order, and an average across unrelated assets does not describe your trade. The site estimates price deviation from public books without placing orders. Funding on a perpetual position is a separate holding cost.
Before and after an order
- Match contract, currency, direction, size and observation time.
- Check that visible depth covers the complete simulated order.
- Confirm your account fee tier and contract size.
- After execution, reconcile the fills, weighted average and actual fees.
Related reading: How to compare funding rates: intervals, direction and position costs · How to read exchange API uptime and incident records · Clock offset and quote age: how to interpret timing data
Rules and sources
Coinbase Exchange · Orders · Measurement method · About this site
These examples are hypothetical, not live prices. Check venue rules and account records for actual charges or execution.
Other guides
How to compare funding rates: intervals, direction and position costs
Compare the same perpetual contract and settlement currency, then check the interval and whether you are long or short. An identical percentage can produce different payments when settlement schedules differ.
How to read exchange API uptime and incident records
Uptime describes the share of successful requests to particular endpoints over a particular period and network route. It does not establish whether you can place an order, withdraw funds or trust a venue with assets.
Clock offset and quote age: how to interpret timing data
A fast response can contain an old quote. Round-trip latency, clock offset and quote age describe different parts of a request. Mixing them can make a clock mismatch look like a delayed market feed.